Bioconversion of post-culture wastewater from farm fisheries for the production of high-value algal biomass

Abstract

Post-consumption water from inland fisheries possesses a tremendous environmental impact on aquatic ecosystems due to their high load of nutrients such as Nitrates, Phosphates, Urea and organic load. Due to the high cost of current water treatment systems, most of the waters from inland fisheries are discharged without any treatment, thus generating a significant environmental impact in rivers of different localities. Cyanobacteria are a group of photosynthetic microorganisms that can grow in different environments including wastewater. Among the most industrially exploited cyanobacteria, Spirulina (Arthrospira) maxima is the most relevant microorganism, due to its capacity to produce large quantities of protein and colourants (especially phycocyanins) for the food and feed industry. The objective of this project is to determine the maximum production capacity of Spirulina in post-consumption waters of fish farming as a system for the treatment of this type of water through the biological capture of the various nutrients and the production of biomass of industrial interest. S. maxima was produced on 3 different media (wastewater + Zarouk, wastewater + K2HPO4, NaNO3, NaHCO3 and wastewater without any modification) for 30 days. Results shown that S. maxima can effectively grow on wastewater supplemented with NaNO3 (2.5 g/L), NaHCO3 (16.8 g/L) and K2HPO4 (0.5 g/L) to obtain up to 1.18 g/L of total biomass and 0.23 g/L of phycocianins. The scaling of culture at 10 L showed a minimal reduction on final biomass and phycocyanin (1.05 and 0.21 g/L respectively), this result indicates that the production of biomass and phycobiliproteins from S. maxima in wastewater from inland fisheries can be a possible candidate for the simplification of biomass and high-value metabolites process production.